As wireless networks evolve and grow in complexity, there are ongoing challenges associated with reaching targeted coverage levels. In modern wireless networks, channel conditions change with time due to changes in the environment between the transmitter and receiver, and user mobility. Radio signals are attenuated as they travel through the air. When a transmitted signal propagates through the air it encounters different objects, and the signal will be attenuated, delayed in time and phase shifted due to reflection, diffraction and scattering. The attenuation caused by distance is modeled as pathloss. The signal variations due to diffraction are modeled as shadow fading (shadowing), whereas the effects of reflections are taken as multipath fading (multipath).
Power is an important resource for wireless devices. To minimize power consumption, power control is employed in the uplink channel between an access node and a wireless device. Power control plays an important role in system throughput, capacity, quality and power consumption. In a wireless multiuser environment, a number of users share the same radio resources. Frequency reuse is an important feature of a cellular system which improves the network capacity. Long-term evolution (LTE) networks support a frequency reuse factor of one to maximize the spectrum 6 efficiency for the uplink and downlink transmissions. The presence of interference cannot be ignored due to this frequency reuse factor. To minimize the effect of interference, Power Control (PC) is used for the LTE uplink. It enhances system throughput performance and reduces interference to other cell users. The use of SC-FDMA in the LTE uplink eliminates interference between users in a cell (intra cell interference). However, the transmissions in neighboring cells are not orthogonal which causes interference between users (inter cell interference). This has a significant effect on the system throughput.
Recently, in an effort to boost coverage and enhance throughput in wireless networks, network operators have proposed deployment of wireless devices capable of transmitting at a maximum allowable transmit power that is higher than a current maximum allowable transmit power of off-the-shelf wireless devices and/or other currently deployed low power wireless devices. As shown in Table 1 below, the maximum allowable transmit power for wireless devices can be defined by the power class of the wireless device.
TABLE 1Power Power Power Power Class 1Class 2Class 3Class 4Wireless Wireless Wireless Wireless Oper-DeviceDeviceDeviceDeviceatingPowerTol.PowerTol.PowerTol.PowerTol.Band(dBm)(dB)(dBm)(dB)(dBm)(dB)(dBm)(dB)Band I31±226±223±221±2Band II——26±223±221±2Band III————23±221±2For example, the maximum allowable transmit power level and tolerance (i.e., power error limits) with which wireless devices can transmit data on a given frequency band or sub-band (e.g., bands I-III) can be specified based on a pre-defined power class (e.g., power classes 1-4 illustrated in Table 1) of the wireless device rather than a physical maximum transmit capability of the wireless device. Off-the-shelf and/or other low-power wireless devices are currently defined in LTE as power class 3 and/or power class 4 wireless devices. Power class 3 and/or power class 4 low-power wireless devices (hereinafter referred to as standard or low-powered wireless devices, with the terms “standard” and “low” being equivalent and defined as any power level that is not “high”) can be configured with a maximum allowable transmit power level of +23 dBm for frequency bands I-III with a nominal power tolerance of ±2 dB (e.g., for E-UTRA bands). High-power class wireless devices (hereinafter referred to as high-powered wireless device) are currently defined as power class 1 or power class 2 wireless devices. Power class 1 and/or power class 2 high-power class wireless devices can be configured with a maximum allowable transmit power level of +26 dBm for frequency bands I-II with a nominal power tolerance ±2 dB (e.g., for E-UTRA bands), as illustrated in Table 1.